This study investigates the sensitivity and specificity of cytology, qualitative, and real-time RT-PCR methods in free cancer cell detection of peritoneal washing from gastric cancer patients. Peritoneal washings were collected from 65 gastric cancer patients for routine cytology and total RNA extraction for qualitative and real-time RT-PCR for CEA. The sensitivity and false-positive rate was 51.1%, 0% for cytology, 48.9% and 5% for qualitative RT-PCR for CEA, and 42.5% and 5% for real-time RT-PCR for CEA. The qualitative and real time RT-PCR results show high concordance rate (89.7%). The highest sensitivity was obtained by the combination of cytology with qualitative RT-PCR for CEA (70.2%). RT-PCR results were positive in 63.6% of cytologic "atypia" cases. Combination of cytology and either of the RT-PCR methods resulted in significantly higher sensitivity than any one of the three methods alone (P < 0.05). There was no definite advantage of the real-time RT-PCR over the conventional RT-PCR.